Boss Michael O’Leary described it as “non-existent, mythical and a misguided invention”. Thousands of travellers’ plans were left in disarray as the ash cloud from Iceland’s biggest volcanic eruption in 50 years forced the cancellation of more than 500 flights in Britain.

The fallout from the Grimsvotn volcano followed severe storms which affected road and rail travel across Scotland on Tuesday.

Would the CAA please take their finger out of their incompetent bureaucratic backsides?

Michael O’Leary

Hundreds of engineers were yesterday working to restore power to homes. Most of the cancelled flights were to and from Scotland and the north east of England as the dense section of the ash cloud worked its way south.

The chaos revived memories of last year’s massive disruption across Europe when another Icelandic volcano caused the cancellation of 104,000 flights affecting 10million passengers.

Since then airlines have been cleared to fly through low and medium density ash clouds – but none have yet sought permission to fly through high concentrations.

But the Geneva-based International Air Transport Association found it “astonishing and unacceptable” that Britain’s aviation regulator did not have its own Cessna planes to gather ash plume data.

Outspoken Mr O’Leary slammed the red zone showing the densest ash concentrations as “mythical” after defiantly sending a plane up in Scottish airspace. His jet flew from Prestwick over Inverness and Aberdeen before landing in Edinburgh.

According to Met Office projections the whole area had been expected to be under a thick ash cloud up to 20,000ft.

Ryanair, which had to cancel nearly 70 flights yesterday, said there had been no visible ash cloud or any other presence of volcanic ash. It also claimed the post flight inspection revealed no evidence of it on the airframe, wings or engines.

Calling for the airspace to be reopened, Mr O’Leary said: “There’s nothing over the skies of Scotland, there is no volcanic ash cloud over Scotland, there’s no volcanic material over Scotland.

“Would the CAA please take their finger out of their incompetent bureaucratic backsides and allow the aircraft back into the skies over Scotland?”

But the CAA said the flight did not go through the high contamination area, and Ryanair was later forced to cancel all Scottish flights after the Irish Civil Aviation authority ruled his planes could not fly.

However, Bill Munro, chairman of leading firm Barrhead Travel joined in the attack saying: “One cannot believe that Ryanair would jeopardise in any way the safety of its passengers or would not tell the absolute truth regarding their test flight details.”

But the CAA said Ryanair had based its test flight on an early prediction – and not on up to date advice to pilots which showed there was no heavy ash concentration in the area of the flight – apart from when it went north and flew at 41,000ft putting it above the cloud.

Later, Glasgow and Edinburgh Airports cancelled all flights for the rest of the day, citing guidance from the CAA. Prestwick Airport reported it had no flights coming in or out of the airport throughout the day.

British Airways grounded planes to and from Edinburgh, Glasgow and Newcastle “as a precaution”.

EasyJet’s website stated that all Scottish flights were cancelled until at least 7pm last night.

Celtic manager Neil Lennon was among the thousands stranded by the chaos, posting a message on Twitter: “Stuck in London because of the ash...looks like am going sightseeing today.” The latest Met Office five-day forecast for the fallout shows most of Britain under a dense high altitude cloud of volcanic ash.

The cloud will be between 35,000ft and 55,000 ft above the whole of Britain including the busiest airports, Heathrow, Gatwick and Stansted subject to the variability of the winds and the volcanic eruption.

Meanwhile, a massive clean-up operation swung into action yesterday as workers cleared fallen trees and restored power lines which had blocked roads and railways.

Engineers were working to restore power to thousands of homes and businesses after storms with winds of up to 130mph battered Scotland.